It is frequently necessary to close an opening in a tubular member either permanently or semi-permanently, that is, to close an opening where a valve is not required or is not desirable. One example of a semi-permanent closure arises when a hot tap is made into a pipeline or a vessel through a fitting connected to the pipeline or vessel. In the typical hot tapping application as utilized in the petroleum industry, a fitting is welded on the exterior of a pipe that has flowing gas or liquid under pressure. A flange is then secured to the fitting and a hot tapping machine secured to the flange. By use of highly specialized equipment, a hole can then be drilled through the wall of the pipe while a gas or liquid continues to flow through it to provide access to the interior of the pipe, such as for inserting equipment to temporarily block flow through the pipe while repairs are being made to it. After the repairs are complete the equipment is removed but the opening that provides communication to the interior of the pipe needs to be closed. Preferably the closure is made in such a way that at some future date access can be again obtained through the fitting to the interior of the pipe. This is just one example of the need for a closure for an opening in a tubular member.
For background information relating to closure devices, reference may be had to the following United States patents:
______________________________________ U.S. Pat No. Patentee ______________________________________ 3,155,116 B. VER NOOY 3,483,894 FINOCCHIARO 3,766,947 OSBURN 4,377,185 KATZ 4,387,740 VANZANT 4,466,550 SULLIVAN 4,576,778 FERREE ET AL. 4,609,209 RALLS 4,693,278 WILSON ET AL. 4,902,043 ZILLIG ET AL. 5,035,266 BENSON ET AL. 5,038,830 ARNAUD 5,437,309 TIMMONS 5,450,765 STOVER ______________________________________